The Chemistry Book

Definitions of Elements

1. An element is a pure substance that cannot be broken down by chemical means.
2. Elements are defined by the number of protons they possess; that is, all atoms of an element have the same atomic number.
3. Elements contain only one type of atom.

Element Symbols

Each of the known elements is given a name and a one- or two-letter abbreviation (symbol). Often this abbreviation is simply the first letter of the element; for example, hydrogen is abbreviated as H, and oxygen as O. Sometimes an element is given a two-letter abbreviation; for example, helium is He. ^[1] Exceptions to this are newer unnamed elements; for example, elements between 111 and 119 are given three letter designations. ^[2]

Rules of Element Symbols

1. The first 1-2 distinguishing letters in the element's name is used for the symbol
2. The first letter is uppercase; the second letter is always lowercase

Learning the Elements

Memorization is an important step to understanding chemistry, however, memorizing every known element is not necessary. Instead, beginning chemists should start memorizing the first 20 elements, representative elements, and elements derived from ancient names. The remaining elements may be found by looking on a periodic table.

Symbols from Ancient Names

Students should memorize all the symbols derived from ancient names:

English name	symbol	ancient name
antimony	Sb	stibium
copper	Cu	cuprum
gold	Au	aurum
iron	Fe	ferrum
lead	Pb	plumbum
mercury	Hg	hydrargyrum
potassium	K	kalium
silver	Ag	argentum
sodium	Na	natrium
tin	Sn	stannum
tungsten	W	wolfram

The First 20 Elements

Happy Henry, the Little Beach Boy, CaN dO FiNe.

Naughty Meghan, the Alpine Sister, Pretends to Ski at ClArK Canyon.

The Element Song

Tom Lehrer provided the chemistry community with a fun way of thinking about the known elements by singing the names of the elements to the tune of I Am the Very Model of a Modern Major General from the musical Pirates of Penzance.

See the flash version on Private Hand for some animated fun.

Table of Elements

Group #	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18
Period
1	1 H																	2 He
2	3 Li	4 Be											5 B	6 C	7 N	8 O	9 F	10 Ne
3	11 Na	12 Mg											13 Al	14 Si	15 P	16 S	17 Cl	18 Ar
4	19 K	20 Ca	21 Sc	22 Ti	23 V	24 Cr	25 Mn	26 Fe	27 Co	28 Ni	29 Cu	30 Zn	31 Ga	32 Ge	33 As	34 Se	35 Br	36 Kr
5	37 Rb	38 Sr	39 Y	40 Zr	41 Nb	42 Mo	43 Tc	44 Ru	45 Rh	46 Pd	47 Ag	48 Cd	49 In	50 Sn	51 Sb	52 Te	53 I	54 Xe
6	55 Cs	56 Ba	*	72 Hf	73 Ta	74 W	75 Re	76 Os	77 Ir	78 Pt	79 Au	80 Hg	81 Tl	82 Pb	83 Bi	84 Po	85 At	86 Rn
7	87 Fr	88 Ra	**	104 Rf	105 Db	106 Sg	107 Bh	108 Hs	109 Mt	110 Ds	111 Rg	112 Uub	113 Uut	114 Uuq	115 Uup	116 Uuh	(117) (Uus)	118 Uuo
* Lanthanides			57 La	58 Ce	59 Pr	60 Nd	61 Pm	62 Sm	63 Eu	64 Gd	65 Tb	66 Dy	67 Ho	68 Er	69 Tm	70 Yb	71 Lu
** Actinides			89 Ac	90 Th	91 Pa	92 U	93 Np	94 Pu	95 Am	96 Cm	97 Bk	98 Cf	99 Es	100 Fm	101 Md	102 No	103 Lr

Element categories in the periodic table Metals Metalloids Nonmetals Unknown Alkali metals Alkaline earth metals Inner transition elements Transition elements Other metals Other nonmetals Halogens Noble gases Lanthanides Actinides
Atomic number colors show state at standard temperature and pressure (0 °C and 1 atm) Solids Liquids Gases Unknown	Borders show natural occurrence Primordial From decay Synthetic (Undiscovered)

Element Notations

Style	Sample	Interpretation
Element name	Neon-20	The element name is followed by the mass number (A).
Element symbol	21Ne	Element symbol with the mass number to the left as a superscript
Isotopic notation	21Ne	Element symbol with the mass number to the left as a superscript and the atomic number as a subscript.

Isotopes

Objectives

1. To learn about the terms isotopes, atomic number, and mass number.

2. To understand the use of the symbol AZX to describe a given atom.

3. To learn about various features of the periodic table.

Dalton and Isotopes

Dalton’s theory tended to revolve around a way to describe the masses of isotopes. The existence of isotopes didn't affect any development because isotopes of a given element have virtually identical chemical properties and they all don’t change chemical reactions. Also, the relative proportions of isotopes are constant, regardless of where they are, and no matter how big or small they may be.

Helium and Isotopes

Isotopes have a fixed number of protons, but many exist with various numbers of neutrons. The sum of the protons and neutrons is known as the mass number. An example of an element with two different masses is helium. It can be 3He with two protons and one neutron or 4He with two protons and two neutrons, and these would be known as the isotopes of Helium. Isotopes can have the same chemical properties, but their weights vary. Something interesting about isotopes is the amount of time it takes for half the atom to decay into a more stable form, also known as half-life. There is naturally an abundant amount of isotopes that exist around us because their half-lives are longer than the age of the earth!

Isotope Decay

There are different ways an isotope can decay. They can do this by beta decay, which is emitting an electron and converting a proton into a neutron. B-decay is emitting a positron anti-electron and converting a proton to a neutron. B+ decay is capturing an atomic electron and converting a proton to a neutron is also known as electron capture decay. Also other isotopes can decay by alpha decay. Alpha decay emits an alpha particle which is really a 4He nucleus. Heavy elements occasionally decay by spontaneous fission, dividing the electron in half. An isotope can decay in several possible ways, often emitting gamma-rays as loose energy. Isotopes can act differently when compared to different forms of radiation.

Hydrogen & Isotopes

To distinguish the isotopes of elements such as Hydrogen, you have to look at the number of neutrons. For example, the three isotopes of hydrogen are hydrogen, deuterium, and tritium. Hydrogen has no neutrons, deuterium has one neutron, and tritium has two neutrons. They all have one proton because protons and neutrons interact making the chemical properties the same.

Isotopes Chemical Properties

Isotopes chemical properties are identical, but have great differences when it comes to nuclear stability. The number of neutrons will be most equal to the number of protons, but a growing neutron is a characteristic of stable heavy elements. The element Tin has the most stable isotopes with ten, and the average is usually 2.6 stable isotopes for each element. Another thing about isotopes is that the atomic masses are rarely even numbers. Some modern uses for isotopes are smoke detections which use Americium-241. Radioisotopes can be used to help understand chemical and biological processes in plants.

Isotopic Notation

You can find the numbers of neutrons, protons, and electrons in an isotope by simply using isotopic notation. A over Z to the left of X is the formula. The letter A represents the Atomic Mass, or the combined total of protons and neutrons. Z is the atomic number, or the number of protons and electrons in a given atom. Knowing what at least one is will end up giving you the other. Finally, X stands for the Element Symbol, or the actual symbol of the element being used. If the number of neutrons is given, you can determine the atomic mass. You have to add the atomic number to the number of neutrons to get the atomic mass.

References

www.chem4kids.com/files/atom_isotopes.html, http://www.colorado.edu/physics/2000/isotopes/index.html, http://hyperphysics.phy-astr.gsu.edu/hbase/HFrame.html, http://www.chem.duke.edu/~sds/cruise_ch/nuclear/uses.html

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Original Drawing / Diagram

A X Z

Definitions

1. Isotopes can be viewed as different versions of atoms, based on different numbers of neutrons.

2. Isotopes are atoms of the same element with different masses caused by differing numbers of neutrons.

Example Problems

1. 8 N A 14 6 + 8 = 14 C  C 6 6

2. 12 N 24 24 24 – 12 = 12 Mg  Mg Z 12

3. ? N 64 64 – 29 = 35 Cu  35 N 29

4. 8 N A 16 8 + 8 = 16 O  O 8 8

5. What sub-atomic particle varies in isotopes? A. Neutrons

State Released Test Question

a. What are isotopes?

b. Isotopes are versions of atoms with different numbers of electrons. c. Isotopes are stagnant atoms with no charge. d. Isotopes are different versions of atoms with different numbers of neutrons. e. Isotopes are radioactive atoms with little charge. A. Isotopes are different versions of atoms with different numbers of neutrons.

Further Reading

• Highbeam Encylcopedia

References

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